This invention relates in general to a method and apparatus for switching telecommunications signals and, more particularly, to such a method and apparatus which implement a hybrid transport capable of handling both synchronous and asynchronous communication protocols.
In existing telecommunication networks, various different communication protocols may be used. One such protocol is known as the virtual tributary (VT) protocol. According to this protocol, which is a synchronous protocol, a given user of a communication path is allocated time slices at predetermined periodic intervals. Another common communication protocol, which is an asynchronous protocol, is known as the asynchronous transport mode (ATM). Yet another asynchronous communication protocol is the Internet protocol (IP). According to each of the ATM and IP communication protocols, a given user of a communication path receives time slices which are not periodic, but which instead occur at variable or random points in time.
Until recently, the amount of asynchronous traffic in telecommunications networks was small in comparison to the amount of synchronous traffic. More recently, however, due in part to the popularity of personal computers and the Internet, the amount of asynchronous traffic traveling through telecommunications networks has been progressively and rapidly increasing. The traditional hardware approach was to provide completely separate switching systems for synchronous traffic and asynchronous traffic. However, as the amount of asynchronous traffic has increased, this has become a less desirable approach. In particular, there has been a progressively increasing demand from network users and telecommunications companies for hybrid switching systems which are capable of efficiently and reliably handling both synchronous traffic and asynchronous traffic.
One existing system uses a line card to terminate a fiber optic path which carries information formatted according to the SONET (Synchronous Optical NETwork) industry standard. According to the SONET standard, information is transmitted in packets known as frames, where each frame includes some overhead information and several data segments. Each data segment includes data formatted according to one of several different industry standard communication protocols, and different data segments in the same frame may conform to different communication protocols. In this existing system, the line card is coupled by respective different interfaces to respective dedicated connectors, where each connector corresponds to a respective communication protocol and can each be detachably coupled to a switching circuit card that effects switching according to that respective protocol. The line card terminates the optical path by converting the transmitted information from an optical format to an electrical format. Further, the line card terminates the SONET communication by demapping the SONET frame, so as to organize the data segments according to the specific communication protocols by which the data is formatted. The line card then routes each data segment to the connector and switching circuit card that correspond to the same communication protocol as that data segment. While this existing approach has been generally adequate for its intended purposes, it has not been satisfactory in all respects.
More specifically, because each connector must be dedicated to a particular communication protocol, extra connectors must be provided for each communication protocol of interest, which leads to a relatively large number of extra connectors of various types in any given system, which in turn increases the overall system size. The larger the system, the more space it takes up in a central facility, a terminal application, or the like. Further, providing separate and different types of electrical interfaces to the respective types of connectors for the various communication protocols has the effect of increasing the complexity and cost of the backplane wiring in the system. Moreover, maintenance of the system is complicated by the fact that maintenance personnel must be careful to plug a given switching circuit card only into the proper connector, not just to ensure proper system operation, but also to avoid possible damage to system circuitry. In addition, due to the fact that each line card not only terminates a fiber optic path, but also has to terminate the SONET frame and then route the data segments to respective different switching circuits, the circuitry of the line cards is relatively sophisticated and expensive.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus which facilitate switching of data according to multiple communication protocols, while minimizing the size, complexity and cost of the system hardware. According to the present invention, a method and apparatus are provided to address this need, and involve switching communication information containing information segments that each conform to one of a plurality of different communication protocols, in particular by: transmitting the communication information through a communication path section which includes a plurality of communication paths, each of the communication paths carrying a respective portion of the communication information; providing a plurality of universal connectors which are each adapted to be selectively detachably electrically coupled to any of a plurality of types of switching circuits, each type of switching circuit carrying out switching according to a respective one of the communication protocols; and causing a switching section to route the information segments which conform to each respective communication protocol through a respective interface to a respective universal connector having detachably coupled thereto one of the switching circuits which effects switching according to that respective communication protocol, the interfaces being effectively the same.